In the ventricular-peripheral arterial coupling, the circulatory system is considered as a whole, the ventricle and artery can be regarded as an elastic system, and the effects thereof are mutually influenced. The diastolic and systolic function of the ventricle can supply blood for internal organs, including the ventricle itself and distal limbs. Since the left ventricle and the aorta can be regarded as a driving pump and a passive pump connected in series, the resistance of the driving pump and peripheral vascular tree will be reflected in the artery waveform curve. When the ventricle and the peripheral arteries are matched and well coupled, three peaks will appear in the pulse wave, which represents the left ventricle, aorta and aortic valve closure, respectively. The rules of ventricular contraction and peripheral arterial coupling can be determined once the ventricular volume and the peripheral arteries' volume and/or pressure information are obtained simultaneously.
Among numerous cardiac function tests, index, stroke volume, and ejection fraction, etc., are influenced by cardiac preload, afterload, and heart rate; thus they cannot be used to reflect specific in vivo (contrary to “in vitro” in this context) ventricular systolic function and myocardial contractility. Plenty of data show that the end-systolic pressure-volume relation plays a significant role in assessment of systolic function status. The Maximum Elastance (Emax) measured by the conventional cardiac catheterization is a slope of the ventricular end-systolic pressure-volume relation line, which is a specific index reflecting in vivo ventricular contractility. However, due to the traumatic problem and expensive price, the cardiac catheterization is difficult to carry out in clinical settings.